1. Field of the Invention
This invention relates to a leak detector, that is, a device which may be used for detecting the presence of a leak in a vessel by measuring the mass concentration of the gas in the vessel when a pressure differential exists between the inside and the outside of the vessel.
2. Description of the Prior Art
The classic method for testing for leaks consists of pressurizing a test piece with air and submerging the test piece under water for a period of time. Leaks can be detected by observation of bubbles emerging at the point of the leak. It has also been known to measure for leaks by pressurizing the test piece to a known pressure, sealing the test piece and then detecting whether or not the pressure changes after a period of time. Any change in pressure indicates a leak. A third method involves the use of tracer gases and in such a method a tracer gas may be introduced into a vessel under pressure. A device which is sensitive to the tracer gas can then be moved about the exterior of the vessel until leakage of the gas is sensed. U.S. Pat. No. 3,585,845 to Cornell et al describes such a system. The above methods of leak detection all have disadvantages which make them unsuitable for mass produced products, in view of the fact that the time involved in making a test is typically quite long. In addition, submersion in water causes additional expense where wet parts or rusty parts are intolerable.
Detection of a change in pressure within a sealed test piece, conventionally has required considerable time and has been sensitive to error due to temperature changes. U.S. Pat. No. 3,085,198 to Briggs et al discloses a system, however, which can measure pressure and detect leaks in pressurized vessels.